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Why is Oahu Hawaii’s most densely populated island?

Why is Oahu Hawaii’s most densely populated island?. Koolau Volcanics. Alluvial saddle. Waianae Volcanics. Recharge – rainfall, fog drip, irrigation water Porosity vs. permeability Freshwater lens (Ghyben-Herzberg Principle 1:40) Caprock Brackish transition zone Saltwater zone

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Why is Oahu Hawaii’s most densely populated island?

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  1. Why is Oahu Hawaii’s most densely populated island?

  2. Koolau Volcanics Alluvial saddle Waianae Volcanics

  3. Recharge – rainfall, fog drip, irrigation water • Porosity vs. permeability • Freshwater lens (Ghyben-Herzberg Principle 1:40) • Caprock • Brackish transition zone • Saltwater zone • Dike impounded system • Wells A-E

  4. What are the sources of Oahu’s water? up to 400 inches/year as low as 10 inches/year

  5. What are the sources of Oahu’s water?

  6. What are the sources of Oahu’s water? Irrigation Fog Drip Rain

  7. How much water actually stays in the ground?

  8. How much water actually stays in the ground? Oahu RECHARGE = 10-50% of rainfall, fog drip, irrigation

  9. Where does the groundwater go?

  10. Pahoehoe and Aa flows

  11. Porosity % of the total volume of the rock that contains pore spaces Permeability the ability of a material to transmit fluid Aquifer Permeable rock strata or sediments that transport groundwater

  12. Porosity and permeability of volcanic material good What impedes groundwater flow on Oahu?

  13. Volcanic dikes create impermeable barriers

  14. Limestone Caprock

  15. What impedes groundwater flow on Oahu? • Volcanic dikes • Limestone caprock

  16. Island aquifers unique: Fresh water floats on salt water Height of groundwater above sea level (water table) Sea level (water table) Freshwater lens Brackish water transition zone Salt water

  17. Ghyben-Herzberg Principle 1 ft 40 ft Height of groundwater above sea level (water table) = 1/40th Freshwater lens thickness (Sea water 1/40th more dense than fresh water)

  18. Volcanic dikes and the limestone caprock cause fresh water to pond in the island’s interior

  19. Geology controls aquifer locations

  20. How do we access these aquifers?

  21. How do pumping rates affect aquifers? • What is relationship between: • Pumping rate • Well water level • Chloride content (salt intrusion) • ???

  22. Chloride content Well water level Pumping rate Fresh water lens is thinning via saltwater intrusion

  23. Excessive pumping thins fresh water lens Water level, 1966-2006 Aiea Well Pumping rates 1901-1980 Halekauwila Well Salt content, 1973-2006

  24. Oahu’s fresh water lens, the source of our drinking water, is thinning Depth to water table increasing Depth to salt water decreasing water table – top surface of water-saturated zone

  25. What’s happening to Hawaii’s population?

  26. What’s happening to Hawaii’s population? Rate of population growth increasing 9.3% increase (Honolulu 4.8%) 5.3% increase (Honolulu 3.3%) 2005

  27. Where is growth happening?

  28. Employment

  29. Oahu Population Growth How will the expected population growth affect groundwater resources ???

  30. Growing population • Increasing groundwater withdrawal • Thinning fresh water lens • What else do we have to protect our groundwater from?

  31. Sample contaminants TCE – metal/dry cleaning fluid DBCP – pesticide EDB – pesticide/fumigant TCP – soil fumigant Dieldrin – insecticide Chlordane – insecticide Carbon tetrachloride – propellant/pesticide Atrazine - pesticide Contaminated drinking water wells on Oahu results from 1995-2005

  32. Pesticides

  33. DBCP (1,2-dibromo-3-chloropropane) Carcinogen Reproductive toxicant Developmental toxicant Endocrine toxicant Gastrointestinal/liver toxicant Neurotoxicant Respiratory toxicant Skin toxicant Top 10% most hazardous compounds Dieldrin Carcinogen Cardiovascular toxicant Endocrine toxicant Gastrointestinal/liver toxicant Immunotoxicant Kidney toxicant Neurotoxicant Reproductive toxicant Respiratory toxicant Top 10% most hazardous compounds

  34. Industrial Solvents: Trichlorethene (TCE) Removes grease from vehicle parts, paint remover Found in Schofield wells in 1985 Carcinogen, cardiovascular toxicant, developmental toxicant, endocrine toxicant, gastrointestinal/liver toxicant, immunotoxicant, kidney toxicant, neurotoxicant, reproductive toxicant, respiratory toxicant, skin toxicant

  35. Drinking water wells serving 25,000 military and 55,000 civilians contaminated with TCE.

  36. Hawaii Superfund Sites Contaminants Fumigants: EDB, DBCP, DCP PCBs, volatile organics, semi-volatile organics, metals Metals, organic compounds, petroleum hydrocarbons Industrial solvent: TCE

  37. Pearl Harbor Superfund Site Soil, groundwater, sediment contaminated with metals, organic compounds, petroleum hydrocarbons

  38. Fuel Additives MTBE – fuel efficiency enhancer, possible carcinogen, nervous system effects, liver & kidney damage, etc.

  39. Where is water table on Oahu?

  40. Leaking Underground Storage Tanks

  41. Irritability, excess salivation, labored breathing, tremors, convulsions, deep depression, anemia, leukemia, damage to liver, kidney, lungs, heart, spleen, adrenal glands; cancer, death Chlordane: pesticide Illegal since 1988 Prior to that 3.6 million lbs/year used in U.S.

  42. Waimanalo (?) Gulch Landfill Ma'ili 200 acres 15 years Nanakuli B 432 acres 15.6 years Makaiwa Gulch 338 acres 25 years Ameron Quarry 391 acres 15 years 80 abandoned landfills on Oahu decorating products (paints, stains, varnish, paint thinners), garden products (pesticides, fungicides, herbicides), vehicle products (engine oil, brake fluid, antifreeze, car batteries), household cleaners (bleach, disinfectant, air fresheners), toiletries (cosmetics, old medicines), batteries from watches, radios, mobile phones, etc. may contain heavy metals like mercury, nickel, cadmium

  43. Golfing in paradise… 14% of tourists lots of locals

  44. Oahu Golf Courses1) Ala Wai Golf Course2) Barbers Point Golf Course3) Bayview Golf Links4) Coral Creek GC5) New Ewa Beach GC6) Ewa Villages Golf Course7) Ford Island Golf Course8) Hawaii Country Club9) Hawaii Kai Golf Courses10) Hawaii Prince Golf Club11) Hickam Mamala Bay12) Honolulu Country Club13) Kahuku Golf Course14) Kalakaua Golf Course15) Kaneohe Klipper GC16) Kapolei Golf Course17) Ko Olina Golf Club18) Koolau Golf Course19) Leileihua Golf Course20) Luanna Hills21) Makaha Valley CC22) Makaha Resort GC23) Mid Pacific CC24) Mililani Golf Club25) Moanalua Golf Club26) Navy-Marine Golf Course27) Oahu Country Club28) Olomana Golf Links29) Pali Golf Course30) Pearl Country Club31) Ted Makalena Golf Course32) Turtle Bay Resort Golf Club33) Waialae Country Club34) Waikele Golf Club35) Walter Nagorski Golf Course36) West Loch Golf Course Average 1000 lbs chemical pesticides per year …also fertilizers, herbicides…

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